When he walked into the T-Mobile Arena ring Saturday night, opponent Brandon Cook, suddenly looked small and doomed. Cook must have known he had a better chance to outrun Usain Bolt than to beat Munguia, who is not quite 22 years old but is 31-0, with 26 knockouts. Cook became No. 31 and 26, in the third round.

“We came here to steal the night and I think we did,” said Fernando Beltran, Munguia’s promoter.

Munguia fought 90 minutes before Canelo Alvarez followed him through the ropes and decisioned Gennady Golovkin to take his WBA and WBC middleweight titles. So Canelo tightly looked up the night. But Munguia became mandatory viewing.

He is 6 feet tall and somehow carries 154 pounds without duress. He is rangy and long, like a modern shortstop. He is the WBO champion at junior welterweight and says he wants to unify the titles. The crowd already recognizes and cheers, the way it did for a redhead from Guadalajara earlier this decade. Munguia will keep Canelo’s circle unbroken, until they meet someday.

It is a succession line that Golden Boy Promotions is building. Preserving it will be the tallest order for Munguia.

The victory over Golovkin was Canelo’s 50th. He is only 28. Six years ago he lost a majority decision to Floyd Mayweather, who was canny enough to schedule Canelo early. That remains Canelo’s only loss. Since then he is 8-0-1. Those nine opponents were a combined 292-14-5 when they fought Canelo.

Golovkin was 37-0 when he engaged Canelo last year. Now he is 38-1-1. In this fight, Canelo did things to Golovkin that no previous middleweight could imagine. He did not try to avoid his power. Instead he junked his clandestine tactics of the first fight and challenged Golovkin, head-up. Yet he still was elusive, reducing Golovkin’s power-shot percentage to 26.6.

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Afterward, Canelo singled out his co-trainers, Chepo Reynoso and his son Eddy . “They’ve been my coaches since I was 13, they took me from nothing,” Canelo said. “I want to keep learning from them.”

Canelo was commanding enough to earn kudos from Abel Sanchez, Golovkin’s trainer who had been a verbal provocateur for months.

“It would be hypocritical for us to complain about the decision,” Sanchez said. “It really was decided by the last round. Canelo fought a very good fight. He was a champion today.”

Ah, but that last round …

Golovkin rocked Canelo with 10 power shots and absorbed only two. He found the rhythmic combinations for which he had been searching.

But judges Dave Moretti and Steve Weisfeld gave the round to Canelo. Give it to GGG and you’ve got a unanimous draw, since Glenn Feldman’s scorecard was 114-114.

“I told Gennady after the eighth round that he was losing, that it was time to pick it up,” Sanchez said. “I thought he fought that way.”

“Canelo stood and fought,” Golovkin said. “He fought a good fight. But that doesn’t mean he controlled the fight. I thought I did that.”

Canelo won because he realized why the last fight was a draw, that he could have won if he’d sunk his heels into the canvas and denied Golovkin the right to dictate terms. And, for all the talk about body-punching, Golovkin was given credit, by CompuBox, for only six body shots against Canelo. He only had eight in the first fight.

“You tell guys what you want them to do, but once they get into the ring they see things you don’t see,” Sanchez said.

“You’re more vulnerable when you go there because it opens you up for counters,” Garcia said. “Canelo was too quick for that to happen. He was sharp. He had no fear, no respect for Golovkin’s power. That’s why he stood up to him.”